The idea in one breath: Light through two slits makes stripes on a wall — like ripples crossing. If another detector learns which slit was used, stripes turn into two blobs. The "eraser" wipes that which-slit note after the wall was hit. Stripes can come back — but only when you keep the erased cases.
Not time travel. The past did not change. You are filtering which events you look at. The wall already got hit; later you decide which hits count.
1 · StripesTwo slits, no label → band pattern on the wall.
2 · TwinsEach flash splits: one to the wall, one to a label reader.
3 · GoneLabel reader learns slit A or B → stripes disappear.
4 · EraserMixer scrambles the label (delayed choice).
5 · BackKeep only erased events → stripes return.
6 · RuleFull stripes OR full path info — not both at once.